The phosphorylation of rhodopsin seems to be associated with newly formed disks and the plasma membrane of the rod outer segment. Newly formed disks are more susceptible to proteolytic enzymes than old disks. The chemical structure of the carbohydrate moiety of rhodopsin has been elucidated as N-acetylglucoaminyl beta 1-2 mannosyl alpha 1-3 (mannosyl alpha 1-6) mannosyl beta 1-4N-acetylglucosaminyl beta 1-4n-acetylglucosamine. GTP binding to rod membranes is stimulated by light. A GTP-binding protein has been solubilized which is distinct from rhodopsin, GTPase and c-nucleotide phosphodiesterae.